Conventionally, a resin plate or a steel plate used in various industrial products has been processed into a thin plate shape so as to reduce the weight of the product.
Therefore, for example, it has been known that a rib is provided at the inside of the resin plate so as to reinforce the resin plate in a thin plate shape.
Also, for example, it has been known that a reinforcing sheet for a steel plate is provided at the inside of the steel plate so as to reinforce the steel plate in a thin plate shape.
For example, it has been proposed that a reinforcing sheet for a steel plate including a constraining layer and a reinforcing layer made of a foamable composition is attached to a body steel plate of an automobile and then, using a high temperature heat (for example, 160 to 200° C.) at the time of electrodeposition coating, the reinforcing layer is allowed to foam and cure, so that the body steel plate of the automobile is reinforced (ref: for example, the following Patent Document 1).